Replica databases can be connected with Periscope to run twice as many queries against the same set of data.
Navigate to the database settings page by clicking on the gear icon at the bottom of the sidebar.
In the database page that opens, click Add Database in the top right:
Enter the replica database credentials, and select the database that the new connection is a replica of:
Once the proper credentials have been entered, clicking the "Add" button will successfully connect the replica database. Queries can now be pointed at multiple replicas of the same master, and Periscope will distribute the queries over them to improve throughput.